Coal liquefaction

ABSTRACT

Coal is liquefied under controlled conditions to produce a coal liquefaction product having a Deashability Index (D.I.) of 10-18 wherein D.I. is the weight ratio of ash free benzene insolubles in the product to ash free carbonaceous matter dissolved and dispersed in the liquefaction solvent times 100. The controlled Deashability Index facilitates separation of insoluble material.

United States Patent 19 Snell Dec. 3, 1974 [5 COAL LIQUEFACTION 3,184,401 5/1965 Gorin 208 8 [75] Inventor: George J. Snell, Fords, NJ. Primary Examiner Delbert E. Gantz [73] Assignee: The Lummus Company, Bloomfield, Assistant ExaminerVeronica OKeefe NJ. Attorney, Agent, or Firm-Mam & Jangarathis [22] Filed: Dec. 29, 1972 1 [57] ABSTRACT [21] Appl' 319637 Coal is liquefied under controlled conditions to produce a coal liquefaction product having a Deashability [52] US. Cl 208/10, 208/8 Index (D.I.) of 10-18 wherein DJ. is the weight ratio [51] Int. Cl C10g l/04 of ash free benzene insolubles in the product to ash [58] Field of Search ,208/8, 10 free, carbonaceous matter dissolved and dispersed in the liquefaction solvent times 100. The controlled [56] References Cited Deashability Index facilitates separation of insoluble UNITED STATES PATENTS materlal- 2,987,465 6/1961 .lohanson 208/10 8 Claims, 1 Drawing Figure,

ggjlvluke Up 1 To 550F 2 2/ 23 25 i 24 9 8$; com Slurrying g fig Sepurotion gg:,' Recovery H2 l0 l5 /7 22 l4 l6 B +900 1 40 32* Stripping Hydro Trecning Product COAL LIQUEFACTION This invention relates to the liquefaction of coal, and more particularly to a new and improved process for liquefying coal to facilitate deashing.

Coal can be converted to valuable products by'subjecting coal to solvent extraction, with or without hydrogen, to produce a mixture of coal extract and undissolved coal residue, including undissolved extractable carbonaceous matter, fusain and mineral matter or ash.

The finely divided mineral matter or ash and unreacted coal must be separated from the coal extract, and in general, this separation step has been the principal draw-back to the successful operation of a coal extraction process. The fine particle sizes encountered in coal solvation processes create numerous difficulties in attempting to use conventional separation techniques, such as filtration, centrifugation or settling.

An object of the present invention is to provide a new and improved process for liquefying coal.

Another object of the present invention is to liquefy coal in a manner which facilitates subsequent removal of insoluble material.

These objects and others should be more apparent from reading the following detailed description of the invention with reference to the accompanying drawing wherein:

The drawing is a simplified schematic flow diagram of an embodiment of the present invention.

The objects of the present invention are accomplished, in one aspect, by controlling the coal liquefaction in a manner such that the subsequent separation of finely divided coal residue is facilitated.

- More particularly, the coal liquefaction is controlled in a manner such that the resulting coal liquefaction product comprised of a liquid coal extract of dissolved carbonaceous matter in a coal liquefaction solvent and insoluble material (ash and unreacted coal), has a deashability index (D.l.), as hereinafter defined, within a specified range. It has been surprisingly found thatby controlling the deashability index of the coal liquefaction product, the subsequent separation of theinsoluble material is greatly facilitated while minimizing the loss of desired coal derived products from the coal extract.

In accordance with the present invention, the coal liquefaction is controlled to produce a coal liquefaction product comprised of carbonaceous matter dissolved in I a coal liquefaction solvent and insoluble material dispersed in the liquefaction solvent having a deashability index (D.I.) from about to about 18, and preferably from about 11 to about 15 wherein:

lbs. ash free benzene insolubles in Product 1bs. moisture ash free (MAF) coal derived carbonaceous matter dissolved and dispersed in the coal liquefaction solvent D.I. X 100 of moisture ash free carbonaceous matter dissolved and dispersed in the liquefaction solvent at the end of the coal liquefaction step.

The coal liquefaction is effected by hydrogenating the coal in the presence of a coal liquefaction solvent by any one of the wide variety of procedures known in the art which may be catalytic or non-catalytic. The catalytic liquefaction may be effected in any one of the wide variety of ways known in the art, including a fixed catalyst bed, fluidized catalyst bed or in an expanded or ebullating bed.

The coal liquefaction solvent may also be any one of the wide variety of coal liquefaction solvents which are used in the art, including hydrogen donor solvents, non-hydrogen donor solvents, and mixtures thereof. These solvents arewell in the art and no detailed explanation with respect to such solvents is required for a complete understanding of the present invention. A liquefaction solvent which is preferably employed in the present invention is a 600-900F. solvent (the'components boil either over the entire range or over only a portion of the range) recovered from the coal liquefaction product and which has not been subjected to hydrogenation subsequent to the-recovery thereof.

The Deashability Index of the liquefaction product is controlled by controlling thebenzene insolubles content of the coal liquefaction product from the hydrotreating (the ash content of the coal is fixed and, accordingly, by controlling the total amount of benzene insolubles the numerator of the index is increased and- /or decreased to thereby increase or decrease the Deashability Index). The amount of benzene insolubles in the coal liquefaction product is best controlled by controlling the space velocity of the hydrotreating for a specified catalyst, operating temperature and hydrogen partial pressure, with an increase in the space velocity increasing the amount of benzene insolubles. The selection of specific temperatures, space velocities, catalyst, hydrogen partial pressure, etc., to produce an amount of benzene insolubles in the hydrotreating product which provides the required Deashability Index is deemed to be well within the scope of those skilled in the art.

In general, the hydrotreating is effected at temperatures which range from about 700F. to about 900F., preferably from about 750F. to about 850F., and pressures from about 1,000 to about 4,000 psig. The liquid hourly space velocity is generally from about 1.0 to about 4.0 hr, and the hydrogen partial pressure from about 800 to about 3,000 psia. The hydrotreating is generally effected in the presence of a suitable hydrotreating catalyst, such as cobalt molybdate, tungsten nickel, sulfide, nickel molybdate, mixtures thereof, etc.

The hydrotreating is generally effected in an ebullating bed, as described in US. Pat. No. 2,987,465 to Johanson.

In accordance with the present invention, by controlling the Deashability Index of the coal liquefaction product from the coal liquefaction step, as hereinabove described, the separation of ash is facilited without excess loss of desired coal derived products, as measured by the ash free +850F. product which is not recovered from the coal. It has been found that a decrease in the Deashability Index below a value of 10 results in a decrease in ash removal and an increase of the Deashability Index to above l8, while effecting acceptable ash removal, results in an increase in the loss of ash free +850F. coal product. 7

The insoluble material is preferably separated from the coal liquefaction product by the use of a liquid promoter having an aromaticity less than that of the liquefaction solvent to enhance and promote the separation of insoluble material and provide a liquid coal extract essentially free of insoluble material.

The liquid which is employed to enhance and promote the separation of insoluble material from the coal liquefaction product is generally a hydrocarbon liquid having a characterization factor (K) of at least about 9.75 and preferably at least about 11.0 wherein:

wherein T is the molal average boiling point of the liquid (R); and G is specific gravity of the liquid (60-F/60F).

The characterization factor is an index of the aromaticity/parafinicity of hydrocarbons and petroleum fractions as disclosed by Watson & Nelson Ind. Eng. Chem. 25 880 1933), with more parafinic materials having higher values for the characterization factor (K). The promoter liquid which .is employed is one which has a characterization factor (K) in excess of 9.75 and which is also less aromatic than the liquefaction solvent; i.e., the characterization factor K of the promoter liquid has a value which is generally at least 0.25, higher than the characterization factor of the liquefaction solvent. g

' The following Table provides representative characterization Factors (K) for various materials:

Table Anthracene Naphthalene 425-500F. Coal Tar Distillate 550900F. Coal Tar Distillate 600-900F. Coal Tar Distillate 400-450F. Coal Tar Distilate Benzene Tetrahydronaphthalene O-xylene Decahydronaphthalene Cyclohexane 425-500F Boiling Range Kerosene n-Dodecylbenzene Propylene Oligomers (pentamer) Cetene Tridecane n-hexane Hexadecane or cetane The liquid which is used to enhance and promote the separation of insoluble material is further characterized by a volume percent distillation temperature of at least about 250F. and a 95 volume percent distillation temperature of at least about 350F. and no greater than about 750F. The promoter liquid preferably has a 5 volume percent distillation temperature of at least about 310F. and most preferably of at least about 400F. The 95 volume percent distillation temperature is preferably no greater than about 600F. The most preferred promoter liquid has a 5 volume percent distillation temperature of at least about 425F. and a 95 volume percent distillation temperature of no greater than about 500F. It is to be understood that the promoter liquid may be a hydrocarbon; e.g., tetrahydronaphthalene, in which case the 5 volume percent and 95 volume percent distillation temperatures are the same; i.e., the hydrocarbon has a single boiling point.

In such a case, the boiling point of the hydrocarbon must be at least about 350F. in order to meet the requirement of a 5 volume percent distillation temperature of at least 250F. and a 95 volume percent distillation temperature of at least about 350F. The promoter liquid is preferably a blend or mixture of hydrocarbons in which case the 5 volume percent and 95 volume percent distillation temperatures are not the same.

The 5 volume and 95 volume percent distillation temperature may be conveniently determined by ASTM No. D 86-67 or No. D 1160 with the former being preferred for those liquids having a 95 percent volume distillation temperature below 600F. and the latter for those above 600F. The methods for determining such temperatures are well known in the art and further details in this respect are not required for a full understanding of the invention. It is also to be understood that the reported temperatures are corrected to atmospheric pressure.

As representative examples of such liquids, there may be mentioned: kerosene or kerosene fractions from paraffmic or mixed base crude oils; middle distillates, light gas oils and gas oil fractions from paraffinic or mixed based crude oils; alkyl benzenes with side chains containing ten or more carbon atoms; paraffinic hydrocarbons containing more than 12 carbon atoms; white oils or white oil fraction derived from crude oils; alphaolefins containing more than 12 carbon atoms; fully hydrogenated naphthalenes and substituted naphthalenes; propylene oligomers (pentamer and higher); tetrahydronaphthalene, heavy naphtha fractions, etc. The most preferred liquids are kerosene fractions; white oils; fully hydrogenated naphthalenes and substituted naphthalenes; and tetrahydronaphthalene.

The amount of liquid promoter used for enhancing and promoting the separation of insoluble matter from the coal liquefaction product will vary with the particular liquid employed, the coal liquefaction solvent, the coal used as starting material and the manner in which the liquefaction is effected. As should be apparent to those skilled in the art, the amount of liquid promoter used should be minimized in order to reduce the overall costs of the process. It has been found that by using the liquid of controlled aromaticity, in accordance with the teachings of the present invention, the desired separation of insoluble material may be effected with modest amounts of liquid promoter. In general, the weight ratio of liquid promoter to coal solution may range from about 0.221 to about 3.0: l preferably from about 0.321 to about 20:1 and, most preferably from about 0.321 to about 1.521. In using the preferred promoter liquid which is a kerosene fraction having 5 percent and percent volume distillation temperatures of 425F. and 500F. respectively, promoter liquid to coal solution weight ratios in the order of 0.4:1 to 06:1 have been particularly successful. It is to be understood, however, that greater amounts of liquid promoter may be employed but the use of such greater amounts is uneconomical. ln addition, the use of an excess of liquid promoter may result in the precipitation or separation of an excessive amount of desired coal derived products from the coal extract. More particularly, as the amount of liquid promoter employed is increased, a greater amount of ash is separated from the coal solution, but such an increased separation is accompanied by an increased separation of desired coal derived products from the coal solution. By using the liquid promoters as herein described, not only may modest amounts of solventbe employed, but, in addition, ash may be effectively separated from the coal solution; e.g., in amounts greater than 99 percent, without an excessive loss of desired coal derived products.

More particularly, coal, such as bituminous coal, on a moisture ash free basis (MAF) may contain from about 5 percent to about percent of insoluble material, such as fusain, and accordingly, at a minimum, from about 5 percent to about 10 percent, of the MAP coal, is lost in the process. In the recovery of coal derived products by a solvation process, the potential product loss is measured by the amount of 850F+ product which is not recovered from the coal in that it is this fraction, which includes insoluble coal material, such as fusain, which can not be recovered from the residual solid product of the coal deashing. In accordance with the present invention, on a MAP coal feed basis, product loss of 850F+ components (on an ash free basis) can be maintained at a value of no greater than about 30 percent, by weight, and preferably no greater than about percent byweight. In general, the loss of 850F+ products, on a MAP coal basis, is from about 10 percent to-about 25 percent, by weight. In addition, the net coal product (the extracted carbonaceous matter, excluding promoter liquid, liquefaction solvent and gas make), hereinafter sometimes referred to as coal product, contains less than about 0.5 percent insoluble material, all by weight. The specific amount of insoluble material which is permitted to be present in the coal product is dependent upon the product standards, and the deashing is controlled in order to provide the required specifications. Based on an Illinois type, the production of a coal product having less than .05 percent, by weight, insoluble-material, corresponds to 99+ percent ash removal but as should be apparent to those skilled in the art, the percent ash removal to provide a coal product having the required minimum amount of insoluble material is dependent upon the initial ash content of the coal. Thus, in accordance with the present invention, the liquid promoter is added to the coal solution in an amount, as hereinabove described, to provide a coal product in which insoluble material is present in an amount of less than about 0.05 percent, by weight, with the loss of 850F+ product being from about 10 percent, to about percent, by weight, preferably from about 10 percent to about 25 percent, by weight, on a MAP coal feed basis; i.e., from about 70 to about 90 percent, by weight, of the MAP coal feed is recovered as either gas make or liquid fuel product.

The Liquid promoter may also be prepared by blending a material having a characterization factor below 9.75 with a material having a characterization factor above 9.75, provided the blend has a characterization factor above 9.75 and the boiling properties, as hereinabove described. The use of blended materials is a convenient manner of regulating the characterization fac- IOI.

As a further alternative, the liquid promoter may be an indigenous promoter which is produced by hydrotreating a portion of the recovered coal product, as described in application Ser. No. 304,320 filed on Nov. 7, 1972.

The separation of the insoluble material from the coal extract is generally effected at a temperature from about 300F. to about 600F., preferably from about 350F. to about 500F., and at a pressure from about 0 psig to about 500 psig, preferably at a pressure from about 0 psig to about 300 psig. It is to be understood that higher pressures could be employed, but as should be apparent to those skilled in the art, lower pressures are preferred. The insoluble material is preferably separated by gravity settling with theessentially insolublefree coal extract being recovered as an overflow and the insoluble material as underflow. In such gravity settling, the amount of underflow should be minimized in order to minimize the loss of heavier products in the underflow. The underflow withdrawal rate to obtain desired results is deemed to be within the scope of those skilled in the art. In general, such a rate is from about 20 to about 25 wt. percent of the total feed (liquefaction product and promoter liquid). The residence time for such settling is generally in the order of from about 0.5 to about 6 hours and preferably from about 0.5 to 3.0 hours.

As another distinct feature of the present invention, the heavier material recovered from the coal extract; e.g., the +8509 or +900F. liquid product, may be further hydrotreated to reduce the sulfur content thereof. In controlling the initial hydrotreating step to produce the required Deashability Index, the hydrotreating may not be sufficient to produce the desired decrease in sulfur content and, in accordance with the present invention the heavier product may be. hydrotreated to further reduce the sulfur content.

The use of a second hydrotreater may also be advantageous in the case where the desired sulfur reduction could not be effected in the initial hydrotreatment. In such a case, the initial hydrotreating is controlled to produce a liquefaction product having the required Deashability Index, but without the required reduction in sulfur content. The required reduction in sulfur content is then effected in a second stage hydrotreatment.

This operation offers the advantage that no liquefaction solvent is required for the second hydrotreatment which permits a reduction in reactorvolume and an increase in space velocity. In addition, the hydrotreating is effected on an ash free feed which permits'th'e use of different operating techniques; e.g., a different catalyst and/or a different mode of operation; a fixed bed as opposed to an expanded bed.

The invention will be further described with respect to an embodiment thereof illustrated in the accompanying drawing. It is to be understood, however, that the scope of the invention is not to be limited thereby.

Referring to the drawing, ground or pulverized coal, generally bituminous, sub-bituminous or lignite, preferably bituminous coal, in line 10 is introduced into a coal solvation and slurrying zone 11 along with a coal liquefaction solvent in line 12. The coal liquefaction solvent may be any one of the wide variety of coal liquefaction solvents used in the art, including both hydrogen donor solvents, non-hydrogen donor solvents and mixtures thereof. These solvents are well known in the art and, accordingly, no detailed description thereof is deemed necessary for a full understanding of the invention. As particularly described, the coal liquefaction solvent is a 600F900F. solvent which is recovered from the coal liquefaction product and which has not been subjected to hydrogenation subsequent to the recovery thereof. The solvent is added to the coal in an amount sufficient to effect the desired liquefac- 20:1, and preferably from about 1.5:1 to about 5:1.

Acoal paste is withdrawn from zone 11 through line 13 and introduced into a coal liquefaction zone 14 .wherein, as known in the art, the coal is converted to liquid products. The liquefaction zone 14 is operated as known in the art and may becatalytic or non-catalytic and may be effected in the presence or absence of added hydrogen. The hydrogenation may be effected in a fixed catalyst bed, fluidized catalyst bed or an expanded or ebullating bed, preferably an expanded bed as described in US. Pat. No. 2,987,465 to Johanson. As hereinabove described, the hydrotreating is controlled to produce a coal liquefaction product having a Deashability Index of from about to about 18. The hydrotreating, as known in the art, reduces the sulfur and nitrogen content of the recovered liquid coal product.

A coal liquefaction product, comprised of a liquid coal extract of dissolved carbonaceous matter in the coal liquefaction solvent and insoluble material (ash and undissolved coal) is withdrawn from the liquefaction zone 14 through line 15 and introduced into a separation zone 16 to separate from the coal liquefaction product at least those materials boiling up to about the 95 volume percent distillation temperature of the liquid to be used for promoting and enhancing the separation of the insoluble material. The separation zone 16 may include an atmospheric or vacuum flashing chamber or tower, and as particularly described separation zone 16 is designed and operated to separate components boiling up to about 550F.

A coal liquefaction product, free of components boiling up to about 550F., withdrawn from separation zone 16 through line 17, is mixed with promoter liquid in line 21 of controlled aromaticity, i.e., the characterization factor of the promoter liquid has a value which is generally at least 0.25 unit greater than the characterization factor of the coal liquefaction solvent. As particularly described, the promoter liquid is a kerosene fraction which has 5 volume percent and 95 volume percent distillation temperatures which fall within the range from about 425500F. and is derived from a naphthenic or paraffmic crude oil.

The combined stream of coal liquefaction product and promoter liquid in line 22 is introduced into a gravity separation zone 23, comprised of a gravity settler which may be any one of those known in the art, wherein an essentially solids free overflow is separated from a solid containing underflow. Although the gravity settler may be any one of those generally known in the art, the settler is preferably of a special type developed for the present invention as described in application Ser. No. 304,319 filed on Nov. 7, 1972.

The overflow essentially free of insoluble material, is withdrawn from separation zone 23 through line 24 and introduced into a recovery zone 25 for recovering promoter liquid and various fractions of the coal extract. The recovery zone 25 may be comprised of one or more fractionators to distill various fractions from the product. As particularly described, the recovery zone is operated to recover a first fraction having 5 and 95 percent volume distillation temperature of from 425 to 500F., which is to be used as the promoter liquid for enhancing and promoting separation of solid material from the coal liquefaction product; a second fraction (500-600F.) which may beemployed asa distillate fuel blendstock; a third fraction (600-900F.) a portion of which may be used as the coal liquefaction solvent in line 12 and a further portion thereof recovered as product and a residual product (+900F) of low ash and reduced sulfur content. The promoter liquid recovered in the recovery zone is admixed with the liquefaction product in line 17 and makeup may be provided through line 26.

The underflow containing dispersed insoluble material withdrawn from separation zone 23 through line 31 is introduced into a stripping zone 32 wherein material boiling, below about 900F. is stripped therefrom and introduced into the recovery zone 25 through line 33. The ash rich stripper bottoms in line 34 may then be subjected to calcination or coking. Alternatively, part of the stripper bottoms may be used as feedstock to a partial oxidation process for producing hydrogen. As a further alternative a portion of the stripper bottoms may be used for plant fuel. These uses and others should be apparent to those skilled in the art from the teachings herein. In accordance with the present invention, the stripper bottoms in line 34 contains from about 10 to about 30 percent, by weight, of the MAF coal. In addition the coal product (the product recovered from zones 16 and 25, excluding liquefaction solvent and promoter liquid) contains less than 0.05 percent, by weight, of insoluble material).

-The residual product (+900F) of low ash and reduced sulfur content recovered in recovery zone 25, in line 40, may be introduced into a hydrotreating zone 41 to further reduce the sulfur content thereof. The hydrotreating is effected, in the absence of a pasting or liquefaction solvent, with hydrogen gas introduced through line 42 as known in the art. The hydrotreating is generally effected in the presence of a suitable hydrodesulfurization catalyst, such as at a temperature from about 600F. to about 850F. and pressures from about 1,000 to about 3,000 psig. The hydrotreated product of further reduced sulfur content is withdrawn from zone 41 through line 43 as a low sulfur fuel or as a blend stock for a low sulfur fuel.

The present invention will be further described with respect to the following examples which further illustrate the present invention, but the scope of the invention is not to be limited thereby. Unless otherwise indicated all parts and percentages are by weight.

EXAMPLE 1 40 wt. percent bituminous coal and 60 wt. percent of a 600900F. coal tar distillate is fed along with hydrogen into an upflow, expanded bed catalytic reactor containing admixed cobalt and nickel molybdate in sulfided form as catalyst. The temperature is 790-850F.; the pressure 1,400 psig; the space velocity 2.3 hr. and the hydrogen feed 23 SCF/lb. coal. The coal product has a Deashability Index of 12.8.

The coal liquefaction product is deashed by settling in a 1500 ml. resin flask using 425500F. boiling range kerosene (K =1 1.9) at a promoter liquid to coal solution weight ratio of 0.75. The settling is effected at a temperature of 3S0F., a pressure of 0 psig, a settling time of 3.8 hours, and an overflow withdrawal of about percent of the feed.

The ash removal based on overflow is 99.7 percent and the loss of +850F. MAF coal as a percentage of MAP coal feed is 27 percent.

EXAMPLE II 40 wt. percent bituminous coal and 60 wt. percent of a 600900F. coal tar distillate is fed along with hydrogen into an upflow, expanded bed catalytic reactor containing cobalt molybdate in sulfided form as catalyst. The temperature is 780-820F.; the pressure 1,400 psig; the space velocity 0.98 hr.; and the hydrogen feed 25 SCF/lb. coal. The coal product has a Deashability Index of 3.22.

The coal liquefaction product is deashed by settling in a 1500 ml. resin flask using 425500F. boiling range kerosene (K=l 1.9) at a promoter liquid to coal solution weight ratio of 0.75. The settling is effected at a temperature of 350F., a pressure of psig, a settling time of 3.8 hours and an overflow withdrawal of about 75 percent of the feed.

The ash removal based on overflow is 96.5 percent and the loss of +850F. MAF coal as a percentage of MAP coal feed is about 18 percent.

This example illustrated that ash removal is not optimized when the Deashability Index is below the range of the present invention.

EXAMPLE III 40 wt. percent bituminous coal and 60 wt. percent of a 600-900F. coal tar distillate is'fed along with hydrogen into an upflow, expanded bed catalytic reactor containing cobalt molybdate in sulfided form as catalyst. The temperature is 780-820F.; the pressure 1,200 psig; the space velocity 1.32 hr.; and the hydrogen feed 25 SCF/lb. coal. The coal product has a Deashability Index of 7.

The coal liquefaction product is deashed by settling in a 1,500 ml. resin flask using 425-500F. boiling range kerosene (K=l 1.9) at a promoter liquid to coal solution weight ratio of 0.75 The settling is effected at a temperature of 350F., a pressure of 0 psig, a settling time of 3.8 hours and an overflow withdrawal rate of about 84 percent of the feed.

The ash removal based on overflow is 97.75 percent.

This example illustrates that ash removal is not optimized when the Deashability Index is below the range of the present invention.

EXAMPLE IV 40 wt. percent bituminous coal and 60 wt. percent of a 600900F. coal tar distillate is fed along with hydrogen into an upflow, expanded bed catalytic reactor containing cobalt molybdate in sulfided form as catalyst. The temperature is 7608l0F.; the pressure 1,200 psig; the spave velocity 3.96 hr.'; and the hydrogen feed 25 SCF/lb. coal. The coal product has a Deashability Index of 28. The coal liquefaction product is deashed by settling in a 1500 ml. resin flask using 425500F. boiling range kerosene (K=11.9) at a promoter liquid to coal solution weight ratio of 0.75. The settling is effected at a temperature of 350F., a pressure of 0 psig, a settling time of 3.8 hours and an overflow withdrawal rate of about 72 percent of the feed.

The ash removal based on overflow is 99 percent and the loss of +850F. MAF coal as a percentage of MAP coal feed is 33.4 percent.

This example illustrates that loss of +850F. product is not optimized when the Deashability Index is above the disclosed range.

The present invention is particularly advantageous in that the coal liquefaction can be effected in a manner which optimizes the subsequent removal of insoluble material by maximizing removal of ash and minimizing the loss of potentially valuable coal products.

Numerous modifications and variations of the present invention are possible in light of the above teachings and, therefore, within the scope of the appended claims the invention may be practised otherwise than as particularly described.

What is claimed is:

l. A process for liquefying coal to produce a coal liquefaction product from which insoluble material is more facilely separated, comprising:

hydrogenating coal in contact with a coal liquefaction solvent to effect liquefaction thereof, said hydrogenation being effected at a temperature of from about 700F to about 900F, a space velocity from about 1.0 to about 4.0 hr. and a hydrogen partial pressure from about 800 to about 3,000 psia to produce a coal liquefaction product comprised of carbonaceous matter dissolved in the coal liquefaction solvent and insoluble material dispersed in the liquefaction solvent having a weight ratio of ash free Benzene insolubles in the product to moisture ash free carbonaceous matter dissolved and dispersed in the coal liquefaction solvent from about 0.10 to about 0.18.

2. The process of claim 1 wherein said hydrogenating is effected in the presence of a catalyst.

3. The process of claim 2 wherein said hydrogenation is effected in an upflow ebullating bed of said catalyst.

4. The process of claim 3 wherein said coal liquefaction solvent boils within the range from about 600F. to about 900F.

5. The process of claim 1 and further comprising:

separating insoluble material from the coal liquefaction product.

6. The process of claim 5 wherein said insoluble material is separated by gravity settling, said gravity settling being effected with the coal liquefaction product in contact with a promoter liquid, said liquid promoter having a 5 volume percent distillation temperature of at least about 250F. and a volume percent distillation temperature of at least about 350F. and no greater than about 750F., said liquid promoter having a characterization factor (K) of at least 9.75, said liquid promoter having a characterization factor greater than said coal liquefaction solvent; said promoter liquid being added in an amount sufficient to promote and enhance gravity settling of insoluble material to produce an overflow essentially free of insoluble material.

7. The process of claim 2 wherein the catalyst is se-v lected from the groupconsisting of cobalt molybdate, tungsten nickel sulfide, nickel molybdate and mixtures thereof.

8. The process of claim 1 wherein said weight ratio is from about 0.1 l to about 0.15. 

1. A PROCESS FOR LIQUEFYING COAL TO PRODUCE A COAL LIQUEFACTION PRODUCT FROM WHICH INSOLUBLE MATERIAL IS MORE FACILELY SEPARATED, COMPRISING: HYDROGENATING COAL IN CONTACT WITH A COAL LIQUEFACTION SOLVENT TO EFFECT LIQUEFACTION THEREOF, SAID HYDROGENATION BEING EFFECTED AT A TEMPERATURE OF FROM ABOUT 700*F TO ABOUT 900*F, A SPACE VELOCITY FROM ABOUT 1.0 TO ABOUT 4.0 HR.-1 AND A HYDROGEN PARTIAL PRESSURE FROM ABOUT 800 TO ABOUT 3,000 PSIA TO PRODUCE A COAL LIQUEFACTION PRODUCT COMPRISED OF CARBONACEOUS MATTER DISSOLVED IN THE COAL LIQUEFACTION SOLVENT AND INSOLUNLE MATERIAL DISPERSED IN THE LIQUEFACTION SOLVENT HAVING A WEIGHT RATIO OF ASH FREE BENZENE INSOLUBLES IN THE PRODUCT TO MOISTURE ASH FREE CARBONACEOUS MATTER DISSOLVED AND DISPERSED IN THE COAL LIQUEFACTION SOLVENT FROM ABOUT 0.10 TO ABOUT 0.18.
 2. The process of claim 1 wherein said hydrogenating is effected in the presence of a catalyst.
 3. The process of claim 2 wherein said hydrogenation is effected in an upflow ebullating bed of said catalyst.
 4. The process of claim 3 wherein said coal liquefaction solvent boils within the range from about 600*F. to about 900*F.
 5. The process of claim 1 and further comprising: separating insoluble material from the coal liquefaction product.
 6. The process of claim 5 wherein said insoluble material is separated by gravity settling, said gravity settling being effected with the coal liquefaction product in contact with a promoter liquid, said liquid promoter having a 5 volume percent distillation temperature of at least about 250*F. and a 95 volume percent distillation temperature of at least about 350*F. and no greater than about 750*F., said liquid promoter having a characterization factor (K) of at least 9.75, said liquid promoter having a characterization factor greater than said coal liquefaction solvent; said promoter liquid being added in an amount sufficient to promote and enhance gravity settling of insoluble material to produce an overflow essentially free of insoluble material.
 7. The process of claim 2 wherein the catalyst is selected from the group consisting of cobalt molybdate, tungsten nickel sulfide, nickel molybdate and mixtures thereof.
 8. The process of claim 1 wherein said weight ratio is from about 0.11 to about 0.15. 